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1.
(Ti, Al)N films have drawn much attention as alternatives for TiN coatings, which are oxidized easily in air above 500 °C. We have investigated the effect of Al content on the oxidation resistance of (Ti1 − xAlx)N films prepared by r.f. reactive sputtering.(Ti1 − xAlxN films (O ≤ x ≤ 0.55) were deposited onto fused quartz substrates by r.f. reactive sputtering. Composite targets with five kinds of Al-to-Ti area ratio were used. The sputtering gas was Ar (purity, 5 N) and N2 (5 N). The flow rate of Ar and N2 gas was kept constant at 0.8 and 1.2 sccm, respectively, resulting in a sputtering pressure of 0.4 Pa. The r.f. power was 300 W for all experiments. Substrates were not intentionally heated during deposition. The deposited films (thickness, 300 nm) were annealed in air at 600 900 °C and then subjected to X-ray diffractometer and Auger depth profiling.The as-deposited (Ti1 − xAlx)N films had the same crystal structure as TiN (NaCl type). Al atoms seemed to substitute for Ti in lattice sites. The preferential orientation of the films changed with the Al content of the film, x. Oxide layers of the films grew during annealing and became thicker as the annealing temperature increased. The thickness of the oxide layer grown on the film surface decreased with increasing Al content in the film. For high Al content films an Al-rich oxide layer was grown on the surface, which seemed to prevent further oxidation. All of the films, however, were oxidized by 900 °C annealing, even if the Al content was increased up to 0.55. 相似文献
2.
D.H. Tassis C.A. Dimitriadis S. Boultadakis J. Arvanitidis S. Ves S. Kokkou S. Logothetidis O. Valassiades P. Poulopoulos N.K. Flevaris 《Thin solid films》1997,310(1-2):115-122
Thin films of polycrystalline β-FeSi2 were grown on (100) Si substrates of high resistivity by electron beam evaporation of Si/Fe ultrathin multilayers and subsequent annealing by conventional vacuum furnace (CVF) and rapid thermal annealing (RTA) for 1 h and 30 s, respectively, in the temperature range from 600 to 900°C. X-ray diffraction, Raman spectroscopy, spectroscopic ellipsometry, resistivity and Hall measurements were employed for characterization of the silicide layers quality in terms of the annealing conditions. For the silicide layers prepared by CVF annealing, although the grain size increase with increasing the annealing temperature, the optimum temperature to obtain the higher material quality (carrier mobility of the order of 100 cm2 Vs−1 and carrier concentration of about 1 × 1017 cm−3) is about 700°C. At higher annealing temperatures, the quality of the material is degraded due to the presence of the oxide Fe2O3. In the case of the silicides prepared by RTA, the quality of the material is improved progressively with increasing the annealing temperature up to 900°C. 相似文献
3.
SnS and SnS2 thin films have been prepared by the dip technique. In this technique, a substrate was dipped into an alcoholic solution of the corresponding chloride and thiourea and then withdrawn vertically at a controlled speed, and finally baked in a high temperature furnace at atmospheric condition. XRD and SEM data suggest that good quality SnS and SnS2 films are obtained at a baking temperature of 300 and 360°C, respectively. Values of band gap for SnS and SnS2 obtained from spectral response of photoconductivity are 1.4 and 2.4 eV, respectively. The indirect allowed band gap values for SnS2 film obtained from optical absorption measurements are 1.95 and 2.05 eV. Open-air annealing of both SnS and SnS2 films at 400°C converts them to transparent conducting SnO2. 相似文献
4.
T. Kanagasekaran P. Srinivasan D. Kanjilal P. Ramasamy 《Materials Research Bulletin》2008,43(4):852-863
The 50 MeV Si ion irradiation-induced modifications on structural, chemical, optical and thermal properties of Vertical Bridgman grown benzimidazole (BMZ) crystals have been studied. The FTIR studies have been used to analyze the variation in various bonds that are associated with the functional groups in the native and the irradiated sample. X-ray diffraction studies reveal the compressive strains that are generated due to irradiation. The effect of irradiation on the conductivity of BMZ crystals has been studied. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The thermal analysis reveals that the melting point remains unaffected and the sample does not decompose as a result of irradiation. 相似文献
5.
The effects of the deposition of ultrathin 57Fe layers on both sides of the NiFe layers in NiFe/Cu multilayers were investigated by focusing on their structural, magnetic and magnetoresistance properties. Conversion electron Mössbauer spectroscopy measurements showed an out-of-plane magnetic anisotropy of the Fe layers. The magnetoresistance curves showed an unusual shape, where up to three peaks were observed. Eight variables computer simulations, based on a phenomenological model that considers bilinear and biquadratic couplings between layers with cubic and in-plane uniaxial anisotropies, were used in order to calculate the best-fitting magnetization curves for the NiFe/Cu and Fe/NiFe/Fe/Cu multilayers. Both model and Mössbauer spectroscopy results showed that it is the rotation of the Fe magnetic moment from out-of-plane to in-plane orientation that provokes the unusual magnetoresistance curve shape. The observed reduction of the magnetoresistance amplitude with the addition of one monolayer of Fe in the NiFe/Cu multilayer was attributed to a less-effective spin-dependent scattering that occurs at Fe/Cu and Fe/NiFe interfaces than at the NiFe/Cu interfaces. 相似文献
6.
In the present work, Fe/Ag superlattices were grown by molecular beam epitaxy (MBE) on MgO(001) single crystal substrates maintained at room temperature or at 423 K during the deposition. The structural properties were carried out using small and high angle X-ray diffraction techniques. The magnetic hysteresis loops with the magnetic field applied parallel or perpendicular to the plane of the films were measured by a superconducting quantum interference device (SQUID) magnetometer in the temperature range 5–300 K. A comparison of the obtained results showed that the heating of MgO substrates leads to a strong interdiffusion and causes a significant modification of structural and magnetic properties of Fe/Ag superlattices. 相似文献
7.
Lithium niobate thin films have been deposited on Pt/Ti/SiO2/Si(100) substrates by Pechini method. Characterization of the initial precursor solutions containing citric acid (CA), niobium and lithium ions has been performed by Fourier transform infrared spectroscopy, Raman spectroscopy and carbon nuclear magnetic resonance spectroscopy. The results indicate that citric acid coordinate to niobium ions to form a niobium-CA complex through one terminal carboxyl group, the hydroxyl group and the central carboxyl group as a tridentate ligand. The thermal decomposition of the Li-Nb precursors gel powder has been studied and the results show that LiNbO3 phase is formed directly from the thermal decomposition of the precursor gel. By heat-treatment at 600 °C for 2 h, polycrystalline LiNbO3 thin films with smooth and crack-free surface could be achieved. 相似文献
8.
The transition from the tetragonal (I4/mcm) to the orthorhombic (Imma) structure associated with a change in A- to CE-type antiferromagnetism in the Pr0.5−xNdxSr0.5MnO3 has been investigated by X-ray diffraction as well as magnetization and resistivity measurements. The transition is found to occur between x=0.1 and 0.2. 相似文献
9.
V. Stancu C. Dragoi V. KuncserG. Schinteie L. TrupinaE. Vasile L. Pintilie 《Thin solid films》2011,519(19):6269-6277
The results of the electric and magnetic measurements performed on PbZr0.2Ti0.8O3-BiFeO3 symmetric structures, deposited on Pt/Si wafers, were compared for different number of layers in order to analyse the effect of interfaces over the macroscopic properties. It was found that the shape and magnitude of the capacitance-voltage characteristic, as well as the shape and parameters of the ferroelectric and magnetic hysteresis, depend on the number of interfaces in the intended multilayer structure. A temperature induced gradual transition from a magnetically disordered spin glass like phase of low temperature to an uncompensated antiferromagnetic phase at room temperature takes place in the BiFeO3 films, under low applied magnetic fields. A partial ferromagnetic like order can be obtained at low temperatures by increasing the field. The observed changes in the electric and magnetic behaviour of the systems were related to an increased degree of disorder for electric dipoles and magnetic moments, due to the increased number of layers and crystallization treatments. 相似文献
10.
The phase relations in CeO2–Eu2O3 and CeO2–Sm2O3 systems have been established under slow-cooled conditions from 1400 °C. The two-phase relations differ as the CeO2–Eu2O3 system showed only two monophasic phase fields, namely F-type cubic and C-type cubic, whereas CeO2–Sm2O3 system showed three phase fields namely F-type cubic, C-type cubic and a biphasic field comprising of C-type cubic and monoclinic phase. An interesting observation of this investigation is the stabilization of C-type rare-earth oxide after Ce4+ substitution, which is attributed to decrease in average cationic size on Ce4+ substitution at RE3+ site. The lattice thermal expansion behavior of F-type solid solution and C-type solid solution in CeO2–Eu2O3 system was investigated by high-temperature XRD. 相似文献
11.
Pd/Ru metallization scheme is fabricated on n-GaN as a Schottky contact, and the electrical and structural properties have been investigated as a function of annealing temperature by current–voltage (I–V), capacitance–voltage (C–V), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. As-deposited Ru/Pd/n-GaN contact yielded Schottky barrier height (SBH) of 0.67 eV (I–V) and 0.79 eV (C–V), respectively. Further, it is observed that the Schottky barrier height increases to 0.80 eV (I–V) and 0.96 eV (C–V) for the contact annealed at 300 °C. However, both I–V and C–V measurements indicate that the barrier height slightly decreased when the contacts are annealed at 400 °C and 500 °C. From the above observations, the optimum annealing temperature for Pd/Ru Schottky contact is 300 °C. Norde method is also employed to extract the barrier height of Pd/Ru Schottky contacts which are in good agreement with those obtained by the I–V technique. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 300 °C compared to the as-deposited contact. Based on the XPS and XRD results, the reason for the increase in SBH upon annealing at 300 °C could be attributed to the formation of gallide phases at the Ru/Pd/n-GaN interface vicinity. The AFM results showed that the overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. The above observations reveal that the Pd/Ru Schottky contact is attractive for high-temperature device applications. 相似文献
12.
Cd1 − xZnxO nanocrystalline thin films with rock-salt structure were obtained through thermal decomposition of Cd1 − xZnxO2 (x = 0, 0.37, 0.57, 1) thin films which were electrodeposited from aqueous solution at room temperature. X-ray diffraction results showed that the Zn ions were incorporated into rock salt-structure of CdO and the crystal lattice parameters decreased with the increase of Zn contents. The bandgaps of the Cd1 − xZnxO thin films were obtained from optical transmission and were 2.40, 2.51, 2.63 and 3.25 eV, respectively. 相似文献
13.
Silvia Ronchetti Elisa Aurelia Turcato Serena Esposito Michele Pansini Daniele Mazza 《Materials Research Bulletin》2010,45(6):744-750
“In situ” high temperature X-ray diffraction under reducing atmosphere is used for the first time to study the thermal stability and transformations of Co- and Fe-exchanged A and X zeolites. TG-DTA and “ex situ” XRD characterization were also carried out.The temperature of incipient crystallization of metallic phase was found to be 700 °C in Fe-zeolites and 800 °C in Co-zeolites. Moreover, ex situ X-ray experiments, after thermal treatment both under inert and reducing atmosphere, revealed the formation of ceramic phases upon the thermal collapse of the zeolitic framework. Metal nanoparticles were obtained by reduction and the size of metal clusters was found to range between 24 and 40 nm. 相似文献
14.
Jianhui Zhang 《Materials Research Bulletin》2009,44(5):1093-4529
A series of solid solution phosphors Ca1−xSrxSe:0.02Ce3+ were prepared using high-temperature solid-state reaction technique. Their diffuse reflectance and luminescent spectra at room temperature were investigated and discussed. The optical band gap Eg energies of CaSe and SrSe were derived. Because of its broad band absorption in the range of 400-500 nm, Ca1−xSrxSe:Ce3+ can suit the application requirements for GaN-based light-emitting diodes (LEDs). The emission wavelength and the coordinates systematic shift from yellowish green to bluish green with an increase in x of Ca1−xSrxSe:Ce3+. Using Dorenbos's empirical equation, the values of energies of the lowest f-d transition absorption E, redshift D and Stokes shift ΔS for Eu2+ in the same host were predicted. The results were in good agreement with the experimental data. 相似文献
15.
The stability of flash-evaporated amorphous Ge2Sb2Te5 thin films has been studied under medium-term temperature treatment (30 - 80 °C, with a step of 10 °C) in ten subsequent heating and cooling cycles. The significant changes in structure and optical properties are reported. The temperature cycling of the films resulted in formation of an isolated 5 - 7 nm nano-crystalline phase in the amorphous phase. The corresponding increase in refractive index and change in optical bandgap energy and sheet resistance are also presented. The formation of Ge2Sb2Te5 nano-crystals (~ 5 - 7 nm) even under temperature below 80 °C could contribute to the explanation of mechanism of resistivity fluctuation (drift) of the “amorphous phase” films. We also show that the optical and electrical properties of flash evaporated Ge2Sb2Te5 thin films are very similar to those reported for sputtered films. 相似文献
16.
Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn2O4 phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 °C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 °C, 50 °C and 80 °C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were correlated with measured electrical properties in order to define optimal processing conditions. 相似文献
17.
M.M. Wu J. Peng D.F. Chen J.S. Fieramosca J. Jorgensen 《Materials Research Bulletin》2007,42(12):2090-2098
The syntheses and structures of Er2−xCexW3O12 were studied. It was found that pure phases could form only for 0.0 ≦ x ≦ 0.4 and 1.5 ≦ x ≦ 2.0. Compounds with 0 ≦ x ≦ 0.4 have the hydrated orthorhombic structure at room temperature and transform to unhydrated orthorhombic one above 135 °C whereas samples with 1.5 ≦ x ≦ 2.0 crystallize in monoclinic structure. Thermal expansion properties of Er2−xCexW3O12 were studied with high temperature X-ray powder diffraction. Samples with 0 ≦ x ≦ 0.4 exhibit negative thermal expansion in temperature range of 200-800 °C and higher cerium content leads to more negative thermal expansion coefficient. However, compounds with 1.5 ≦ x ≦ 2.0 show positive thermal expansion owing to the edge-sharing polyhedra. 相似文献
18.
S.J. Barker R.S. Williams M.J. Steer M.J. Ashwin P.N. Stavrinou T.S. Jones 《Thin solid films》2007,515(10):4430-4434
GaNxAs1−x multiple-quantum-well (MQW) samples (x ≤ 0.025) grown by molecular beam epitaxy have been studied by photoluminescence (PL) spectroscopy, high-resolution X-ray diffraction (HR-XRD), secondary-ion mass spectrometry (SIMS) and ultra-high-resolution infrared local-vibrational-mode (IR LVM) spectroscopy in order to determine their compositional and structural properties. Compositional data from PL spectroscopy and HR-XRD, derived using simple models of the superlattice structure, show good agreement. SIMS depth profiles show that the wells are triangular, and are wider and shallower than predicted, with nitrogen present in the barrier layers. A comparison between SIMS and HR-XRD suggests the presence of interstitial nitrogen for samples with the highest nominal concentrations. By contrast, IR LVM measurements demonstrate that substitutional nitrogen incorporates linearly with increasing nitrogen fraction. 相似文献
19.
20.
Gd-doped BiFeO3 polycrystalline ceramics were synthesized by solid-state reaction method and their dielectric and magnetic properties were investigated. X-ray diffraction pattern showed that Bi1 − xGdxFeO3 (x = 0, 0.05 and 0.1) ceramics were rhombohedral. The Gd substitution has suppressed the usual impurity peaks present in the parent compound and we obtained single phase Bi0.9Gd0.1FeO3 ceramic. Gd substitution reduced the antiferromagnetic Néel temperature (TN) in Bi1 − xGdx FeO3. An anomaly in the dielectric constant(ε) and dielectric loss(tan (δ)) in the vicinity of the antiferromagnetic Néel temperature (TN) was observed. Ferroelectric and magnetic hysteresis loops measured at room temperature indicated the coexistence of ferroelectricity and magnetism. The room temperature magnetic hysteresis loops were not saturated, but the magnetic moment was found to increase with increase in Gd concentration. 相似文献